A so-called field assembly optical connector as an optical connector which allows assembly-work to be easily performed with respect to a tip of an optical fiber on site is well known. In the related art, as a field assembly optical connector, a field assembly optical connector is known, which includes a short optical fiber (bare optical fiber, and hereinafter, also referred to as a built-in optical fiber) which is inwardly inserted into and fixed to a ferrule, and a mechanical splice type clamp portion which is provided on a rear side opposite to a front end surface of the ferrule for butting (for example, refer to FIGS. 2 to 5 of Patent Document 1).
The clamp portion of the field assembly optical connector includes a base member, a pressing member, and a plate spring which elastically biases the pressing member toward the pressing member. A rear end portion of the built-in optical fiber is disposed between the base member and the pressing member of the clamp portion. Another optical fiber (for example, an optical fiber core wire, and hereinafter, also referred to as an insertion optical fiber), which is inserted between the base member and the pressing member of the damp portion from a rear side opposite to the ferrule side, can be butt-connected to a rear end of the built-in optical fiber. In the Held assembly optical connector, the rear end portion of the built-in optical fiber, and a tip portion of the insertion optical fiber which is butt-connected to the rear end of the built-in optical fiber are held between the base member and the pressing member of the damp portion so as to be fixed by elasticity of the plate spring, and the rear end portion of the built-in optical fiber is assembled to the lip of the insertion optical fiber.
In the field assembly optical connector, in order to decrease connection loss, a liquid refractive index matching agent such as silicone-based grease is provided on a butt-connection portion between the built-in optical fiber and the insertion optical fiber (for example, refer to FIG. 16(c) of Patent Document 1).
In addition, in the field assembly optical connection, it is suggested that a light-transmitting solid refractive index matching material formed of a polymer material is be provided on the rear end of the built-in optical fiber, and the insertion optical fiber and the built-in optical fiber having tips abutting on the solid refractive index matching, material are be optically connected to each other via the solid refractive index matching material (for example, refer to FIGS. 7(a) and 7(b) or the like of Patent Document 1).